The present invention relates to an apparatus for coating a primary package. More particularly this invention concerns the coating of an inside wall of a syringe body.
A standard disposable syringe comprises a tubularly cylindrical syringe body having a front end provided with a cannula or needle. The body is provided internally with a piston that defines with the front end a compartment that is filled with a medicament. A plunger connected to the piston can be pushed in to express the medicament from the body. The body is typically made of class 1 hydrolytic glass and the piston of a suitable elastomer.
It is important that the piston move easily in the body so that the medicament can be expressed smoothly or in small doses. Thus it is known to coat the inside surface of the syringe with a silicone oil.
The silicone-oil coating must be uniformly applied to the inner body wall and normally also to the outer surface of the piston. This coating must also be as thin as possible in order to avoid droplets from clogging the cannula.
It is therefore an object of the present invention to provide an improved apparatus for coating an inside surface of a syringe body or the like.
Another object is the provision of such an improved apparatus for coating an inside surface of a syringe body or the like which overcome the above-given disadvantages, that is which forms a very thin and uniform coating, and that are quite simple and inexpensive to use.
The coating apparatus according to the invention has an applicator ring having an outer surface and a system for supplying at least the outer surface of the applicator ring with a coating of silicon oil. This coated ring is displaced from a rear end to a front end of the body with the ring in continuous annular engagement with the inside wall thereof so as to transfer the oil from the ring to the inside wall. A scraper ring is then displaced from the front end to the rear end of the body with the scraper ring in continuous annular engagement with the inside wall so as to scrape excess silicone oil from the inside wall.
The rings are both mounted according to the invention n a rod formed with a passage opening at the applicator ring and connected to the silicone-oil supply. This rod is formed with respective radially outwardly open grooves carrying the rings and the rings are elastomeric O-rings. The passage opens into the groove of the applicator ring at a plurality of offset locations to ensure that the applicator ring is uniformly coated over its entire annular surface.
The groove of the scraper ring according to the invention has a width substantially greater than a diameter of the scraper ring and the rod is provided with a retaining washer received in the scraper-ring groove. The scraper ring lies between the washer and the applicator-ring groove.